Arrangement in electric air blast circuit breaker



June 23, 1953 H. FoRwALD 2,643,315

ARRANGEMENT IN ELECTRIC AIR BLAST CIRCUIT BREAKER Filed Aug. 15, 195owww s s* Patented June Z3, 1953 ARRANGEMENT IN ELECTRIC AIR BLASTCIRCUIT BREAKER Haakon Forwald, Valhalla, Ludvika, Sweden, assignor toAllmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a Swedishcorporation Application August 15, 1950, Serial No. 179,506 In SwedenAugust 18, 1949 (Cl. G-148) 3 Claims. 1

In electric air blast circuit breakers the porcelain insulatorsenclosing the breaking elements and also the porcelain cylinderscarrying the circuit breaker and conducting compressed air to thebreaking points often are lined with a cylinder of organic material inorder to prevent the porcelain insulators or cylinders from beingexposed to stresses due to an inner overpressure. In such arrangementshumidity has been condensed on the inner wall of the porcelain cylinderswith a resultant corresponding decrease of their Hash-over strength.

The present invention has for its object to provide an arrangement bywhich such disadvantage can be avoided. According to the invention, aspace between the inner lining cylinder and the outer porcelain cylinderis brought into communication with the space inside the lining cylinderby means of ducts allowing compressed air to get access to the saidspace between the cylinders, and in addition this space is brought intocommunication with the external air by ducts which may be provided withspring-loaded valves or restricting valves so set in relation to thebefore mentioned ducts that a flow of compressed air can take placethrough this intermediary space, but so that a pressure is maintainedwhich is considerably lower than the pressure inside the lining cylinderbut, however, two or more times higher than the external atmosphericpressure dependent upon the stress which may be allowed on the porcelaincylinder. Instead of arranging restricting valves in these ducts, theircross-section may be so chosen in relation to the cross-section of theother ducts that the desired pressure is attained.

The arrangement according to the present invention has the importantadvantage that although the porcelain cylinder is subjected to internalpressure from the extinguishing'fluid, it,

is relieved from excessive pressure by the inner cylinder and the ventswhereby uid pressure passes from the interior of the inner cylinder tothe space between such cylinder and the porcelain cylinder and wherebythe pressure within said space is vented to the atmosphere and is thusprevented from reaching an excessive value that might damage theporcelain cylinder, but is permitted to attain a pressure of more thantwo atmospheres.

The invention is illustrated on the accompanying drawing applied on anextinguishing chamber for an air blast circuit breaker. On the drawing,I designates the inner lining cylinder which is made from paper treatedwith suitable waterproofing and insulating material or a similarmaterial. 2 is the outer porcelain cylinder and 3 is the space betweenthe cylinders which by ducts 4 is in communication with the space insidethe cylinder I and by ducts 5 in communication with the external air. 6designates a spring-loaded valve for each of the ducts 5. 1 designatesthe stationary contact of the circuit breaker, which is arranged in thecover 8 of the extinguishing chamber. 9 is the movable contact of thecircuit breaker, which is actuated by a piston movable in the cylinderIl'l but not shown on the drawing. ll is a cap arranged above theblow-out opening in the contact 1.

In spite of the fact that the invention is illustrated as applied on anextinguishing chamber, it is, however, also applicable on other placesin an air blast circuit breaker in order to protect a porcelain cylinderagainst excessive inner overpressure by arranging inside of it a liningcylinder made of a material more resistant than the ceramic Y material.

I claim as my invention:

l. In an electric air blast circuit breaker, means enclosing the airblast for the breaker elements, comprising an outer ceramic insulatingcylinder, an inner cylinder of organic material spaced from the saidouter cylinder and exposed on its inner surface to the fluid pressure ofthe circuit breaker, ducts for the passage of fluid pressure from theinterior of the said inner cylinder to the space between the cylinders,said ducts being in direct communication with the air blast, andrestricted ducts for the passage of fluid pressure from said space tothe outer air, the restriction through the. latter ducts being such thatthe pressure within said space is considerably lower than the pressurewithin the inner cylinder and is at least twice that of the outer air.

2. Means according to claim 1, comprising spring loaded valve means forrestricting the passage of fluid from said space to the outer air.

3. In an electric air blast circuit breaker,

means enclosing the air blast for the breaker elements, comprising anouter ceramic insulating cylinder, an inner cylinder spaced from andconcentric with said ceramic cylinder and forming an inner space exposedto the full pressure of the air blast and an outer annular space betweensaid cylinders, at least one vent for the passage of fluid from saidinner space to said an nular space in direct communication with the airblast, and at least one vent for the escape of uid from said annularspace to the atmosphere, said Vents being so dimensioned as to HAAKONFORWALD.

References Cited in the file of this patent UNITED STATES PATENTS NameDate Lerstrup Dec. 20, 1949 Number

